Most of the public is aware that the Multiple Listing Service is a private resource where Real Estate Professionals list properties available for sale. Recently, the public has been able to access some of that information on such sites as Realtor.com, Zillow.com, Trulia.com and others.
Once a property is sold and the transaction has closed, the selling price is posted to the listing in the Multiple Listing Service and eventually on the public property records for the county.
Over time, the MLS has become a huge database on closed sales, containing much more information on individual homes than can be gleaned from the public record. This information is only available to real estate agents who are members of the local Multiple Listing Service.
Your agent can provide you with the closed sales data from the local MLS to help determine your offer price.